Laser applications in neurosurgery

Abstract

The "false start" of the laser in neurosurgery should not be misconstrued as a denial of the inherent advantages of precision and gentleness in dealing with neural tissue. Rather, early investigators were frustrated by unrealistic expectations, cumbersome equipment, and a general ignorance of microtechnique. By the early 70s, microneurosurgery was well established, surgical laser equipment for free hand and microlinked application had been developed, and a more realistic view of the limitations of the laser had been established. Consequently, the late 70s really heralded the renaissance of the laser in neurosurgery. Since then, there has been an overwhelming acceptance of the tool in a variety of clinical situations, broadly categorized in five groups. 1. 1)|Perhaps the most generally accepted area is in the removal of extra-axial tumors of the brain and spinal cord. These tumors, benign by histology but treacherous by location, do not present until a significant amount of neurological compensation has already occurred. The application of additional trauma to the neural tissue, whether by further tumor growth or surgical manipulation, frequently results in irreversible damage. Here, the ability of the laser to vaporize tissue, in a fairly hemostatic fashion, without mechanical or thermal damage to sensitive surrounding tissues, is essential. 2. 2)|The ability to incise delicate neural tissue with minimal spread of thermal destruction to adjacent functioning tissue makes the laser the ideal instrument when tumors deep under the surface are encountered in the brain or spinal cord. Thus, the second group of applications is in the transgression of normal neural structures to arrive at deeper pathological tissue. 3. 3)|The third area of benefit for the laser in neurosurgery has been in the performance of neuroablative procedures, calling for deliberate destruction of functioning neural tissue in a controlled fashion. Again, the precision and shape confinement of the destructive beam makes the laser superior to all conventional destructive instruments. 4. 4)|The coagulative properties of certain chromophoric lasers has allowed a new attack on certain vascular tumors and malformations of the brain and spinal cord which had been operated only with trepidation or not at all. Early reports are sobering but encouraging. 5. 5)|Finally, the use of the laser with tissue photosensitization, albeit it in its infancy, offers great promise. This is particularly true in the case of primary brain cancer, where the infiltration of tumorous tissue among normal pathways precludes the classical oncologic surgery practice of resection of a "safe margin". The ability to track and destroy these cells, without affecting adjacent cells, may be the greatest single contribution of the laser to neurosurgery in the future. The present applications of the laser are relatively crude by comparison with what is expected. Endoscopic laser surgery, both vascular and subarachnoid, will diminish morbidity and improve results. From the exotic treatment of aneurysms and arteriovenous malformations of the brain to the mundane care of herniated disks of the spine, it is anticipated that the laser will play an important role. The use of a laser, coupled with computerized imagining devices, will allow increasing precision in arrival to and treatment of deep seated lesions of the brain, brainstem, and spinal cord. The use of different wavelengths, perhaps in the X-ray and ultraviolet spectra, will allow increasing precision with decreasing invasion. Manipulation of wavelength, time, and treatment area will allow subcellular surgery, perhaps in the treatment of personality disorders and movement disorders as well as epilepsy. Tissue welding will allow heightened regenerative and recuperative powers to be exploited. The possibility of laser biostimulation must also be considered. In short, it appears that the future of the laser in neurosurgery is limited only by the imagination of the surgeons. Certainly, the opportunity to exploit new wavelengths offered by the FEL is the key to the future. © 1985.